KATRIN - Karlsruhe Tritium Neutrino Experiment - measuring sub-eV neutrino masses G. Drexlin, FZ Karlsruhe for the KATRIN Collaboration International Europhysics Conference on High Energy Physics EPS-HEP Aachen, July 17-23, 2003 International Collaboration: 60 people, 12 institutions, 5 countries (CZ, D, RU, UK, US) U Bonn – JINR Dubna* – Daresbury Lab – FH Fulda – U & Forschungszentrum Karlsruhe – U Mainz – NPI Rez – RAL – UW Seattle – UW Swansea – INR Troitsk - motivation - major components : molecular tritium sources, spectrometers - sensitivity & project schedule

Motivation I : particle physics valididate or largely rule out models w. quasi-degenerate mass eigenstates Mixings and mass splittings by -oscillation studies, fundamental -mass scale by ß-decay and 0 ßß KATRIN sensitivity Science objectives of KATRIN perform high resolution & high statistics measurement of ß-spectrum close to 18.6 keV endpoint of T 2 m i [eV]

Motivation II : cosmology role of ‘s as hot dark matter – fix or constrain m (  ) S.W. Allen et al, astro-ph/  m = 0.7 eV (best fit) Cosmological limits for  m are model-dependent: D.N. Spergel et al, astro-ph/  m < 0.69 eV (95%CL) need lab measurement! Science objectives of KATRIN perform high resolution & high statistics measurement of ß-spectrum close to 18.6 keV endpoint of T 2

status of present tritium experiments Troitsk Mainz gaseous T 2 -source quench-condensed solid T 2 -source both experiments have reached their intrinsic limit of sensitivity analysis , 2001 analysis 1998/99, 2001 electrostatic retarding spectrometers with magnetic adiabatic collimation see previous talk by Christine Kraus

experimental observable in ß-decay is m aim : improve m by one order of magnitude (2 eV  0.2 eV ) requires : improve m by two orders of magnitude (4 eV 2  0.04 eV 2 ) problem : count rate close to ß-end point drops very fast (~  E 3 ) last 10 eV : 2 x / last 1 eV : 2 x of total ß-activity improve statistics : - stronger tritium source (factor 80) (& larger analysing plane, Ø=10m) - longer measuring period (~100 days  ~1000 days) improve energy resolution : - large electrostatic spectrometer with  E=1 eV (factor 4 improvement) - reduce systematic errors : - better control of systematics, energy losses (reduce to less than 1/10) 2 2 scaling factors for next-generation experiment

10 m20 m5 m5 m 25 m5m KATRIN Layout KATRIN will be located on the site of FZK at Tritium Laboratory Karlsruhe TLK is worldwide unique, for ITER tritium fuel cycle TLK

10 10 ß-decays/s

Main spectrometer – industrial design study Stainless steel vessel ( Ø = 10 m & l = 22 m ) on HV potential, minimisation of background rate : p < mbar (XHV!) main technological challenge of KATRIN, addressed recently at X-VAT Workshop, Bad Liebenzell, April 2003

KATRIN Sensitivity MC spectra for 3 years with  (bg) = 10 mHz: statistical accuracy for optimised measuring point distribution:   (m 2 ) = eV 2 m( ) < eV (90%CL) m ( ) < eV (95%CL) all systematic errors :  ( m 2 ) = eV 2 statistical & systematic errors contribute ~ equally

KATRIN Sensitivity m( ) < 0.2 eV (90% CL) no -mass signal – KATRIN sensitivity : evidence for  -mass signal – KATRIN discovery potential : m( ) = 0.35 eV (5  ) m( ) = 0.30 eV (3  ) MC spectra for 3 years with  (bg) = 10 mHz:

1 2 3  3 2 1

KATRIN time schedule 1/2001first presentation at internat. workshop Bad Liebenzell 6/2001formal founding of KATRIN Collaboration 9/2001submission of Letter of Interest (hep-ex ) BMBF funding astroparticle physics 5/2002International KATRIN review panel, UK joins Collaboration background studies, R&D works, design optimisation 5/2002International KATRIN review panel, UK joins Collaboration 2003 Proposal submission, pre-spectrometer tests, tender for transport section & cryo supply,

KATRIN - hardware status pre-spectrometer: first major KATRIN system component will be operational soon with 2 superconducting magnets vacuum and electromagnetic tests, background studies inspection of weld seams

KATRIN time schedule 1/2001first presentation at internat. workshop Bad Liebenzell 6/2001formal founding of KATRIN Collaboration 9/2001submission of Letter of Interest (hep-ex ) BMBF funding astroparticle physics 5/2002International KATRIN review panel, UK joins Collaboration background studies, R&D works, design optimisation 5/2002International KATRIN review panel, UK joins Collaboration 2003 Proposal submission, pre-spectrometer tests, tender for transport section & cryo supply, 2003/04funding applications & reviews: HGF, DOE, PPARC, RAS set up of T 2 loop, transport section, spectrometer, detector 2006/07commissioning of major components 2007first measurements of entire system

Conclusions KATRIN – a next generation tritium ß-decay experiment: the only model-independent kinematic measurement with sensitivity to sub-eV neutrino masses - no signal: m  < 0.2 eV (90% CL.) sensitivity - signal : m =  discovery potential  first substantial funding: construction works have started ! tight project schedule with aim for first measurements 2007